Use a MAPPING FILE. This file type contains two columns - one for the source variables and values and one for the destination variable name and values to map the source values to.
The application allows users to use the key words @ELSE and @COPY.
@ELSE, value -> Maps all values (not mapped already) to "value", e.g. 1-> "value", 2 -> "value", 3 -> "value", etc.
@ELSE, @COPY -> Maps all values (not mapped already) to current value. e.g . 1 -> 1, 2 -> 2, 3 -> 3, etc.